3 sets or had 3 sets crack!!!!!! That is a total bullshit rumor period. The only sets we have ever had come back were early ones that were only welded on the inside and ground back too far. Since they have been welded on the inside and outside we have not had any issues. The manifolds we sell are made in a special booth made for Inconel welding and they are gas purged. The manifolds are built by a guy that builds formula one headers.